Underfeed stoker



March 10, 1936. c. H. HALL UNDERFEED STOKER Filed Dec, 11, 195o 3 Sheets-Sheet l INVENTOR mer/cf H HALL ATTORNEY C. H. HALL UNDERFEED STOKER Filed Dec.

March I1o, 1936.

11, 1930 3 Sheets-Sheet 2 INVENTOR CMT/cf h. HALL 75m/fm ATTORNEY c. H. HALL UNDERFEED STOKER Filed Deo.

March l0, 1,936.

3 Sheecs-Sheet 3 INVENTOR foffr/cfHHA/.L

ATTORN EY Patented Mar. 10, 1936 UNITED STATES PATENT OFFICE UNDERFEED STOKER Application December 11, 1930, serien so. 501,481'

19 claims. (ci. 11o-45) This invention relates to burners for solid fuel and more particularly` to a burner of the underfeed.V Stoker type similar to that shown in the Hall et al. Patent 1,675,548.

In the 'use of burners of the underfeed type in which the fire pot is stationary it has been found that cracks form in the bed of the burning fuel with the result that air escapes more rapidly through these cracks causing high stack losses and necessitating the supplying of a greater quantity of air to the burner to obtain complete combustion. It has alsobeen found that where the rim of the re pot isstationary, masses of matted clinker build up at the dges of the fire pot and where the furnace is small, as in the household furnaces, these pieces of matted clinker often bridge over the space betweenthe rim and the lining of the furnace and so prevent the proper removal of the ashes and clinkers.

It has also been found that ne particles of fuel dust pass through the perforations in the fire pot and fall to the bottom of the casing surrounding the re pot. 'I'hese particles are objectionable not only in that they soon clog up the air conduit and interfere with the proper supplying of air to the burners, but they also present a hazard in that they may be easily' ignited, because of their flne state of subdivision and the excess of air present, from the heat radiated .from the re pot. It is an ,object of the present invention to provide an improvement in this type tof underfeed burner and to avoid the above objectionable features. It is a further objectto provide improvedrneans for gently agitating the fuel`at the surface of the fire bed and to provide means for evenly distributing the ashes as they are discharged from the fire pot and for preventing the building up of masses of clinker on the rim of the re pot. It is also an object of the invention to -provide means for automatically discharging any ne particles of fuel or ash which may be deposited within the chamber surrounding the fire pot. Other objects will become' apparent.

In describing the invention referencel will be made to the drawings inrwhlch Figure 1 is a' order to illustrate the driving mechanism. Figure 4 is a vertical section taken on the line 4-4 of Figure 3. Figure 5 is a vertical section taken on the line 5-5 of Figure 4.

The invention is described in connection with a heating unit in which solid fuel is fed from a hopp\r I0 outside of the furnace II to the burner positioned within the furnace II and in which air is supplied for the combustion in the burner from an air blower I2. `The ashes from 111e burner are removedfrom the furnace pit by a conveyer I3 in the conduit I4 and are lifted in the elevator I5 so that they will fall into an ash receiving can I 6, also outside of 'the furnace. It will be apparent, however, that the invention may be utilized in other heating units and it is not intended to restrict it to the particular embodiment described.

The fuel to be consumed in the burner may bn fed to it by means of a continuously or intermittently Arotating spiral conveyor I1 on a shaft I8, which is driven by any suitable driving mechanism, for example, such as described in thelHall et al. Patent 1,638,396 or theWightman Patent 1,703,130. This conveyor is en- Y closed within a pipe or conduit I9 which is connected at its outer end to the fuel hopper I0 Y and at its inner end to an elbow shaped conduit member 20 for changing the direction of the fuel vre pot. A suitable packing ring 2'I may be inserted between the edge of the re pot 22 and the frame 23. A ring 28 extending around the and carrying it upwardly into the lower section 30 periphery of the frame 23, is supported from the upper surface of that frame and forms the outer rim of the burner unit.

bearing ring 24 to prevent .leakage of air at this point and is held in position by gravity. In order to prevent displacement of the upper portion of the burner when the fire pot is inverted during installation or transportation, the

' lugs 29, 29, shaped to extend over a lip on the outer surface of the frame 23, are fastened around the upper portion of the casing 25 by means of bolts 30.

'able bushing (not shown) at the outer surface of the elbow shaped conduit 28 and a bevelled spur gear 3| is fixed to the end of the shaft. This spur gear meshes with a bevelled` spur gear 32 xed to a vertical stub shaft 33 supported in the bearing 34. A gear 35 is fixed to the upper end of the shaft 33 and meshes with a ring gear 36 which is xed to or integral with the inner surface of the frame 23 supporting the upper section of the fire pot.

The sections of the re pot are completely enclosed within the frame 23 and the casing 25, the latter being in communication with an annular air conduit 31 which surrounds the fuel conveying pipe I9. The conduit 31 is connected to the air blower I2 through the conduit 38. upper and lower sections of the i'lre pot contain perforations 39, 39, extending around the nre pot, which perforations permit air from the blower I2 to pass through the fuel for the combustion in the burner.

The lower portion of the casing 25 is shaped to provide an elongated cylindrical depression 40 in which a rotatable discharge valve is located. This valve is constructed with cylindrical end portions 4I, 4I, adapted to bear upon cylindrically shaped bearing surfaces in the depression 40. These end portions are connected by vanes 42 arranged as indicated more clearly in Figure 5. An open slot 43 in the bottom of the cylindrical depression 48 extends the length of the vanes 42, and the latter are so arranged that at least two vanes are at all times in contact throughout their lengths with the cylindrical surface on opposite sides of the slot 43.

A lever 44 is xedto the base of the gear 3| for rotation with the shaft I8. This lever is so positioned that at each rotation of the shaft I8 its lower extremity 45 contacts with the upper portion of one of the vanes 42 throughout a sufficient arc to move such vanes a distance that will insure contact between the lever 44 and a succeeding vane shaft I8.

'I'he valve shown is an integral unit which may be removed, if necessary for cleaning, etc.V

and 2 or in one having a rectangular lining or a' cylindrical lining, as illustrated by the dotted line 48 in Figure 3.

In operating my improved underfeed stoker, which is particularly adapted for use in'small domestic furnaces such as are commonly used in heating homes, the shaft I8 is rotated to force the fuel up through the fire pot at such av rate that the fuel is completely burned before being discharged from the rim 28 of the re pot, the required air being supplied through the perfora tions 39, 39. This rotation of the shaft I8 rotates the frame 23 upon the bearing 24 together with the upper section of the fire pot which is suspended from the frame. By this rotation of the upper section of the fire pot the fuel in the re bed is moderately agitated to insure complete combustion and to avoid the formation of cracks in the body of the re bed.

`This rotation also inhibits the formation of large masses of clinker in the fire bed and if such masses are formed so as to extend beyond Thel upon the next rotation of the' the rim of the re pot sumciently to strike the Walls of ,the furnace, as illustrated by the dotted line 50 in Figure 1, they will be scraped off lby striking the corrugated, angular or smooth wall of the furnace. The clinkers knocked off in this manner and the ashes discharged from the fire pot will be evenly distributed and will fall onto the directing plates I which will guide them to the opening 52 at the inner end of the ash remover conduit I4 where they will be conveyed by the screw conveyor I3 to the bottom of the elevator l5 and through that to the ash receiving can I6, for example, as described in the v tion of this valve through the lever 44, these ne particles will be automatically discharged through the slot 43. With the arrangement of vanes illustrated in the drawings, vanes extending on opposite sides of the slot 43 will at all times be in contact with the edges of the depression 48 so that the air Iblown into the casing may not escape through the slot 43.

Although I have described the invention in connection with a unit in which the upper section of the fire pot and the rotating valve are driven by the fuel feeding shaft, these parts may also be driven by some other means, such, for example, as by a suitable driving connection from the ash removing shaft. In referring to a particular construction and arrangement of parts in describing the invention, it is not in tended to limit the invention to the particular features illustrated, it being apparentthat it may be applied in many modified forms by one skilled in the art. The terms used in describing and claiming the invention have been used in an illustrative sense and not as terms of limitations, and it is intended that all equivalents of these terms Ibe included within the scope of the appended claims.

What I claim is:

1. A burner unit of the underfeed type, comprising a perforated fire pot and a' spiral conf veyor adapted `to supply fuel to the lower .por-

tion of the nre pot, a casing surroundingsaid fire pot and communicating with a source of air supply, an aperture in the lower portion of said casing, a valve for" discharging solid particles positioned to close said aperture and having radial vanes contacting with the casing -on opposite sides of the aperture whereby the valve always maintains the aperture sealed to prevent the discharge of air therethrough, and a. lever xed for rotation with the shaft of the .spiral conveyor and adapted to intermittently rotate said valve with each rotation of the shaft.

2. A burner of the underfeed type, comprising a perforated fire pot and a spiral conveyor for supplying fuel to the lower portion of the re pot, a casing surrounding said fire pot and com-A municating with a source of air supply, said casing having a cylindrically shaped depression and an elongated slot in said depression, a valve for discharging solid particles, said valve having cylindrical ends adapted to bear upon the surface of the depression and having radial vanes so positioned that at all times during the rotation of the valve the outer ends of vanes will contact with the cylindrical surface of the depression on opposite sides of the slot, thereby sealing the slot to prevent discharge of air therethrough, and a lever fixed for rotation with the shaft of the spiral conveyor and adapted to contact with a vane of the valve to rotate the same a sufficient distance toy assure contact with a succeeding vane upon further rotation of the shaft.

3. A burner unit comprisingL an underfeed vfire pot having a xed lower section Vextending burner, the steps comprising passing the fuel upwardly through the lower main portion of the fuel bed to the combustion zone without substantial movement of the fuel particles relative to each other and regularly rotating the upper portion of the fuel bed in accordance with the feed of fuel to the burner.

5. In the burning of fuel in an underfeed burner, the steps comprising passing the fuel upwardly through the lower main portion of the fuel bed to the combustion zone, without substantial movement of the fuel particles relative to each other and giving the upper portiorof the fuel bed a regular gentle rotary motion relative to the lower portion throughout the period of operation of the burner.

6. A burner unit of the underfeed type comprising a fire pot, a conveyor adapted to supply fuel to the lower portion of the fire pot, said fire pot comprising a perforated lower fixed section and a rotatable upper section having perforations extending substantially to its lower edge, and meansfor supplying air to the fuel in the lower and upper sections.

7. A method for burning fuel in an underfeed burner, comprising progressing the fuel upwardly through the lower main portion of the fuel bed to the combustion zone with the minimum of movement of the fuel particles relative to each other, continuing the movement of the fuel particles upwardly through the combustion zone while gently agitating them in accordance with the progressive supplying of fuel to the fuel bed.

3. A burner unit of the underfeed type, comprising a fire pot, a conveyor adapted to supply fuel to the lower portion of the fire pot, said fire pot having a lower fixed sectionextending substantially to the combustion zone and a rotatable upper section having ,air inlets extending sub.

stantially to its lower edge, said upper section providing a rotatable outer rim for the unit over the outside edge of which the solid particles of combustion are discharged, and means for rotating the said upper section. v

9. A burner unit of the vunderfeed type, comprising a fire pot, a conveyor adapted to supply fuel to a fixed lower section of the fire pot,

which lower section extends substantially to tion providing arotatable outer rim for the unit,

and means for rotating the said upper section 'at a definite rate dependent upon the rate of feed of fuel by the conveyor.

10. A burner unit of the underfeed type, comprising a fire pot having a fixed lower sec.- tion extending substantially to the combustion zone and adapted to receive fuel from a conveyor and direct it upwardly to the combustion zone without substantial agitation, said fire pot also having an upper section containing air inlet perforations substantially to its lower edge and providing a rotatably mounted outer rim over which the solid particles of combustion are discharged, and means for rotating said rim in accordance with the rate of feed of fuel to the me pot. i

111. A burner unit of the underfeed type, comprising a fire pot, a conveyor adapted to supply fuel to the lower portion of the fire pot, said fire pot consisting of a lower fixed section extending upwardly from the end of the fuel conveyor and a rotatable upper section containing air apertures substantially to its lower edge, means for rotating said upper section in' accordance with the feed of fuel to the burner, and

means for supplying air to said upper section.

12. A burner unit of the underfeed type, comnrising a fire pot, a conveyor adapted to supply fuel to the lower portion of the fire pot, said fire pot consisting of a lower fixed section extending upwardly from theend of the fuel conveyor and having air inlet apertures and a rotatable upper section containing air apertures extending substantially to its lower edge, means for rotating said upper section in accordance with the feed of fuel to the burner and means for supplying air to said upper and lower sections.

13. A burner unit as defined in claim 1l in which the fuel conveyor is operated intermittently.

14. A method for burning fuel in an underfeed burner, comprising progressing a core of fuel upwardly into the combustion zone with the minimum of movement of the fuel particles relative to each other, continuing the movement of the core of fuel particles upwardly through the combustion zone, while subjecting the outer portion of the core to rotary motion to gently agitate the outer layer thereof in the combustion zone.

1511 A burner unit of the underfeed type, cornprising a perforated fire pot, a conveyor adapted to supply fuel to the lower portion of the re pot, a casing surrounding the fire pot and conthe casing, without releasing the pressure within said casing, and means for actuating said discharge means in accordance with the rate of fuel supply.

16. A burner unit of the-underfeed type, comprising a perforated flre pot, a spiral conveyor adapted to supply fuel to the lower portion of the flrepot, a casing surrounding the fire pot and connected to a source of air under pressure above atmosphericl pressure, a rotatable valve positioned in the casing for discharging fine particles of ash or fuel deposited in the casing, without reducing the pressure within the casing, and means actuated by the fuel conveyor for rotating said valve.

17. A burner unit of the underfeed type, comprising a perforated fire pot, a conveyor 'adapted to Supply fuel to the lower portion of the ilre, pot, a rotatable upper section of the fire pot and means for rotating said upper section. a casing surrounding the fire pot and connected to a source of supply of air under pressure above atmospheric pressure, means to discharge ne particles of ash or fuel deposited in the casing, without releasing the pressure within said casing, and means for actuating said discharge means in accordance with the rate of fuel supply.

18. A burner unit of the underfeed type, comprising a perforated fire pot and a conveyor adapted to supply fuel to the lower portion of the re pot, a casing surrounding said fire pot and communicating with a source of air supply underpressure above atmospheric pressure, an aperture in the lower portion of said casing, a rotatable valve for discharging solid particles, positioned to close said aperture and having vanes contacting with the casing on opposite sides of the aperture for maintaining the aperturesealed at all times by the valve and preventing discharge of air therethrough, and means for rotating said valve in accordance with the rate of fuel supply.

19. A burner of the underfeed type, comprising a perforated re pot, a conveyor for supplying fuel to the lower portion of the re pot, a casing surrounding said fire pot and communicating with an air blower, said casing having a .cylindrically shaped depression and an elongated slot in said depression, a valve for discharging solld particles, said valve having cylindrical ends adapted to bear upon the 'surface of the depression and having radial vanes so positioned that at all times during the rotation of the valve the outer ends of the vanes will contact with the surfaces of the depression on opposite sides of the slot, for sealing the slot to prevent discharge of air therethrough, and means for rotating said valve in accordance with the rate of fuel supply.

' CORTICE H. HALL. 

